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Volcanoes

Volcanoes. Shield Volcanoes. Basaltic magma - from oceanic crust – very dense Shield shaped- more flat and rounded than other volcanoes – wider than tall Very quiet non-explosive eruption - Lava erupts from the rift zones or faults on the surface of the cone. Exists as a shield volcano

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Volcanoes

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  1. Volcanoes

  2. Shield Volcanoes • Basaltic magma - from oceanic crust – very dense • Shield shaped- more flat and rounded than other volcanoes – wider than tall • Very quiet non-explosive eruption - Lava erupts from the rift zones or faults on the surface of the cone

  3. Exists as a shield volcano • One of the most active volcanoes on Earth • Towers at a height of 4,190 feet above sea level • 1,000 year old lava envelopes the exterior of this volcano KILAUEA • January 3,2003 – 20 year old birthday of eruption that is still going on – Longest eruption known in Earth’s existence

  4. Hot Spots • Hot Spots: Not all volcanoes develop along plate boundaries. Sometimes magma works its way up through earth’s lithospheric plates. • Areas where this occurs is called a hot spot. • Hot spots appear to be stationary but are they really? ______ Why? ______________________________________________________________________________________________________. • What is an example of a hot spot? __________________________

  5. Volcanic Hot Spot Audio and Visual click here to view and listen to how hot spots are created

  6. Cinder Cone Volcano Characteristics • Characteristics- • Granitic lava- only continental crust • “Narrow” bases and the steepest sides • Pyroclastic (aka - tephra) explosions - mixtures of hot, dry rock fragments and hot gases – VERY EXPLOSIVE

  7. Paricutin • Now stands at a height of 10,400 ft. (3170 meters) • Only one eruption in history—lasted from 1943 to 1952 • Inactive since then • Once cinders erupted, the cone was slowly built up and added to over the years in size • A cinder cone volcano • Located in Mexico • February 20, 1943—Farmer noticed bulge growing in cornfield-within week grew to 100 meters in height • Within five months of the first eruption, the town was evacuated and lay covered in ash and lava

  8. Composite Volcanoes • Made of granitic and basaltic lava • Tall and Wide Mountains - “Middle sized volcano” • Tephra (pyroclastic) and lava flows (at different times)…Can be quiet or very explosive • Examples: Mount Rainier, Mount St. Helens, Mount Shasta, Mount Hood

  9. Mount St. Helens • Example of a composite volcano • Located in the state of Washington, USA • First estimated eruption occurred about 10,000 years ago • Summit stands at 8,363 feet • 57 people died in the 1980 eruption • Also the most examined eruption in recent history • Most recent eruption was in 1990 • Oldest rocks on mountain = 40,000-50,000 years old • 1980 eruption is one of the most powerful eruptions by Mt. St. Helens in its history

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